REMOVAL & INSPECTION
- Remove the cylinder head(s) from the vehicle as previously outlined.
- Using a suitable valve spring compressor, compress the valve spring and remove the valve keys using a magnetic retrieval tool.
- Slowly release the compressor and remove the valve spring caps (or rotators) and the valve springs.
- Fabricate a valve arrangement board to use when you remove the valves, which will indicate the port in which each valve was originally installed (and which cylinder head on V6 models). Also note that the valve keys, rotators, caps, etc. should be arranged in a manner which will allow you to reinstall them on the valve on which they were originally used.
- Remove and discard the valve seals. On models using the umbrella type seals, note the location of the large and small seals for assembly purposes.
- Thoroughly clean the valves on the wire wheel of a bench grinder, then clean the cylinder head mating surface with a) a soft wire wheel, b) a soft wire brush, or c) a wooden scraper. Avoid using a metallic scraper, since this can cause damage to the cylinder head mating surface, especially on models with aluminum heads.
- Using a valve guide cleaner chucked into a drill, clean all of the valve guides.
- Reinstall each valve into its respective port (guide) of the cylinder head.
- Mount a dial indicator so that the stem is at 90° to the valve stem, as close to the valve guide as possible.
- Move the valve off its seat, and measure the valve guide-to-stem clearance by rocking the stem back and forth to actuate the dial indicator.
- Measure the valve stems using a micrometer, and compare to specifications, to determine whether stem or guide wear is responsible for excessive clearance.
Consult the Specifications tables earlier in this section.
All machine work should be performed by a competent, professional machine shop.
Using a valve grinder, resurface the valves according to specifications in this section.
A minimum margin of 1 / 32 " should remain after grinding the valve. The valve stem top should also be squared and resurfaced, by placing the stem in the V-block of the grinder, and turning it while pressing lightly against the grinding wheel. Be sure to chamfer the edge of the tip so that the squared edges don't dig into the rocker arm.
After machine work has been performed on the valves, it may be necessary to lap the valve to assure proper contact. For this, you should first contact your machine shop to determine if lapping is necessary. Some machine shops will perform this for you as part of the service, but the precision machining which is available today often makes lapping unnecessary. Additionally, the hardened valves/seats used in modern automobiles, may make lapping difficult or impossible. If your machine shop recommends that you lap the valves, proceed as follows:
- Invert the cylinder head, lightly lubricate the valve stems, and install the valves in the head as numbered.
- Coat valve seats with fine grinding compound, and attach the lapping tool suction cup to a valve head.
Moisten the suction cup.
- Rotate the tool between the palms, changing position and lifting the tool often to prevent grooving.
- Lap the valve until a smooth, polished seat is evident.
- Remove the valve and tool, and rinse away all traces of grinding compound.
VALVE GUIDE SERVICE
The valve guides used in any of the X-Car engines are integral with the cylinder head, that is, they cannot be replaced.
Refer to the previous "Valves-Removal and Installation" to check the valve guides for wear.
Valve guides are most accurately repaired using the bronze wall rebuilding method. In this operation, "threads" are cut into the bore of the valve guide and bronze wire is turned into the threads. The bronze "wall" is then reamed to the proper diameter. This method is well received for a number of reasons: a) it is relatively inexpensive, b) offers better valve lubrication (the wire forms channels which retain oil), c) less valve friction, and d) preserves the original valve guide-to-seat relationship.
Another popular method of repairing valve guides is to have the guides "knurled". The knurling entails cutting into the bore of the valve guide with a special tool. The cutting action "raises" metal off of the guide bore which actually narrows the inner diameter of the bore, thereby reducing the clearance between the valve guide bore and the valve stem. This method offers the same advantages as the bronze wall method, but will generally wear faster.
Either of the above services must be performed by a professional machine shop which has the specialized knowledge and tools necessary to perform the service.
VALVE SEAT SERVICE
The valve seats are integral with the cylinder head on all engines. On all engines the seats are machined into the cylinder head casting itself.
Machining of the valve seats should be referred to a professional machine shop.
VALVE SPRING TESTING
Place the spring on a flat surface next to a square. Measure the height of the spring, and rotate it against the edge of the square to measure distortion. If spring height varies (by comparison) by more than 1 / 16 in. or if distortion exceeds 1 / 16 in. replace the spring.
In addition to evaluating the spring as above, test the spring pressure at the installed and compressed (installed height minus valve lift) height using a valve spring tester. Spring pressure should be - 1 lb. of all other springs in either position.
VALVE & SPRING INSTALLATION
Be sure that all traces of lapping compound have been cleaned off before the valves are installed.
- Lubricate all of the valve stems with a light coating of engine oil then install the valves into the proper ports/guides.
- If umbrella-type valve seals are used, install them at this time. Be sure to use a seal protector to prevent damage to the seals as they are pushed over the valve keeper grooves.
If O-ring seals are used, don't install them yet.
- Install the valve springs and the spring retainers (or rotators), and using the valve compressing tool, compress the springs.
- If umbrella-type seals are used, just install the valve keepers (white grease may be used to hold them in place) and release the pressure on the compressing tool. If O-ring type seals are used, carefully work the seals into the second groove of the valve (closest to the head), install the valve keepers and release the pressure on the tool.
If the O-ring seals are installed BEFORE the springs and retainers are compressed, the seal will be destroyed.
- After all of the valves are installed and retained, tap each valve spring retainer with a rubber mallet to seat the keepers in the retainer.